The present invention relates generally to the fabrication of tufting yarn utilized in the manufacture of shag carpeting and the like. More particularly, the present invention relates to a method of and apparatus for producing plied yarn from either continuous filament yarn or from staple yarn in one continuous operation wherein single ends of yarn are plied with one another and twist-set in a bulked condition.
The fabrication of tufting yarn for shag carpeting and the like from either continuous filament or spun staple yarn is conventionally effected by a "batch" process in which single ends of yarn are joined to one another and processed in a number of independent and discontinuous steps. The steps of this process in general are: (a) twisting each single end of yarn about its own longitudinal axis, for example to the extend of 3 turns per inch in the "Z" direction; (b) plying the twisted single ends with one another with an equal amount of twist but in the opposite, i.e. the "S," direction, so that the initial "Z" twist is removed from each of the single ends; (c) skeining the plied yarn by winding the latter on a swift; (d) tumbling the plied yarn in the presence of moist heat, e.g. steam at atmospheric, to develop the inherent bulk in the yarn; (e) twist-setting the plied yarn in an autoclave wherein the yarn is subjected to high-temperature pressurized steam; (f) drying the yarn in the presence of dry heat; and (g) deskeining the yarn and winding it upon a tube.
One of the disadvantages of this batch process is the need for the above-recited numerous and time consuming steps for the yarn after the starting ends have been plied to one another. Moreover, the initial twisting of the single ends of yarn independently of one another before they are plied together leads to another disadvantage. When the pre-twisted single ends are plied to one another, with a ply twist generally equal but opposite in direction to the singles twist, they should lose the previously imparted twist and return to the producer's twist, i.e. a twist of virtually zero. However, since each single end of yarn, after having been given its initial twist, is normally stored for a period of time, often many hours prior to being plied, the single ends develop a memory and a tendency to revert back to the initial twist after the plying operation. Thus, the single ends which form the plied yarn, tend to flare or separate from one another rather than remain in a predictable twist-retentive condition necessary for high quality shag carpeting unless they are twist-set at a high temperature. Such high temperature twist-setting tends to affect the uniform dyeability of the plied yarn.